The ratings and overall good reviews have caused the creators to say there probably will be another miniseries, but for it to work they'll probably have to get Mickey and Martha involved to flesh out the numbers.
This was originally what they said they were going to do before Children of Earth, so I'm not sure why they weren't along. Probably had the budget cut or something so they couldn't afford them.
That or Martha calling the Doctor for help wouldn't have fit with the dark themes of the storyline.